Magnetrons



H- SIXSMITH Dec. 18, 1956 MAGNETRONS 2 Sheets-Sheet 1 Filed Feb. 14,1952 H- SIXSMITH Dec. 18, 1956 MAGNETRONS 2 Sheets-Shet 2 Filed Feb. 14,1952 United States Patent MAGNETRONS Herbert Sixsmith, Reading, England,assignor to English Electric Valve Company Limited, London, England, aBritish company Application February 14, 1952, Serial No. 271,527

Claims priority, application Great Britain February 19, 1951 2 Claims.(Cl. BIS-39.67)

This invention relates to magnetrons and has for its .object to provideimproved magnetrons of high efiiciency, simple construction and capableof delivering high powers at very high frequencies.

According to this invention a magnetron comprises a hollow cavityresonator within which is at least one cathode and at least two anodesin such mutual relationship as to constitute a split anode magnetronsystem, said system being so positioned and arranged with respect tosaid cavity resonator that, when in operation, it excites a standingwave therein and said cavity resonator being provided with means for thewithdrawal of useful power therefrom.

The means for the withdrawal of useful power may take any of a varietyof forms, for example, a loop inserted in the cavity resonator or aconcentric line or wave guide output circuit.

The invention is illustrated in the accompanying drawings in whichFigure 1 is a schematic sectional elevation and Figure 2 is a schematicend view of one embodiment. Figs. 3 to 8 inclusive are schematic viewslike Fig. 2, of further embodiments.

In the form of construction shown in Figs. 1 and 2 there is provided,off-set within a cylindrical cavity resonator 1, an electrode systemconsisting of a rectilinear cathode 2 axially within two similar anodes3 each shaped like a segment of a cylinder with lineally extendingspaced edges. The cathode 2 is parallel to and spaced a desired distancefrom the axis of the cylinder 1 and the split anode magnetron systemconsisting of the said cathode 2 and the anodes 3 extends over thegreater part of the length of the cavity. The whole arrangement is'suchthat operation of the said split anode system as in the normal wayexcites an H011 standing wave in the cavity resonator. This is indicatedconventionally in broken lines in Fig. 2. Output energy is taken offfrom the cavity resonator in any manner known per se such as through thecoupling means shown at 33.

Fig. 3 shows a modification suitable for use where higher power outputsare required. In Fig. 3 there is a ring of similar cathode and doubleanode systems each as above described. As shown the cathodes 2 are allparallel to one another and to the axis of the cavity resonator 1 andare equally spaced along an imaginary ring having the cavity resonatoraxis as a center. Each cathode 2 located is within two anodes 3 just asin Figs. 1 and 2 with the lineal edges of the semi-cylindrical parts ormembers of anodes 3 spaced on opposite sides of diametrical linesthrough the cavity resonator 1. The cathodes and the semi-cylindricalparts or members of anodes 3 are supported in conventional manner withrespect to cavity resonator 1 through wires and spacers of conventionalconstruction.

In a preferred and simpler construction shown in Fig. 4 and suitable foruse on frequencies of the order of 30,000 mc./s. or more the segmentalanodes 3 of the embodiment of Fig. 2 are replaced by rods 31 runningparallel Patented Dec. 18, 1956 to the cathodes 2, each rod serving as acommon anode to two adjacent split anode magnetron systems consisting oftwo cathodes '2'and the common anode rod 31. Thus, as shown in Fig. 4there maybe as many rods 31 as there are cathodes 2, the rodsalternating with the cathodes along, and at right angles to, animaginary ring the axis of which is constituted by the axis of thecavity 1, each rod 31 being mid-way between two cathodes 2 and eachcathode being mid-way between two rods 31.

In a further modification of the arrangement of Fig. 4 shown in Fig; 5the cathodes 2 and rod-anodes 31 are spaced at equal intervals along andat right angles to, concentric rings having the axis of the cavityresonator 1 as a center, the cathodes 2 being in one ring, for example,the outer one, and the rods 31 in the other, and the radii to thecathodes being mid-way between the radii to the rods.

In these constructions, as will be obvious, the direct currentcirculating round the cathodes under the influence of the electrostaticfields between the anodes and cathodes and the applied magnetic field,not indicated, which, of course, is crossed with respect to them. Theprimary function of the anodes being merely to collect electrons whichhave lost energy, the exact orientation of the electrostatic fieldbetween each anode and cathode with respect to the high frequency fieldshould not be of major importance so that precise electrode location inthis respect should not be a requirement. The anodes may, however, havesecondary elfects by introducing local disturbances of the highfrequency field in their immediate neighborhoods but these disturbancesmay be expected to have favorable influences on electron motion in theconstructions described.

In a further modification shown in Fig. 6 the anodes 31 and cathodes 2are again in separate concentric rings and equally spaced along them buteach anode is on a common radius with a cathode instead of being betweentwo of them as in Fig. 5.

In still further modifications three concentric rings of electrodes areused, an intermediate ring of equally spaced cathodes 2 being arrangedmid-way between two other rings of equally spaced anode rods 31, thesaid anode rods being either midway between the radii on which thecathodes lie as shown in Fig. 7 or on the same radii, not illustrated.

The multiple rod anode embodiments above described and illustrated maybe modified as typified in Fig. 8 by replacing each adjacent pair ofanode rods situated on the same circle by a segmental anode 32 lying onthe said circle, opposite ends of each segment being, in operation, atpotentials of opposite simultaneous sign and adjacent ends of adjacentsegments being also at potentials of opposite simultaneous sign. This isconventionally indicated in Fig. 8 by plus and minus signs against a fewof the anodes. In the construction of this nature shown in Fig. 8 thereis a ring of segmental anodes 32 lying in a circle having the axis ofthe cavity resonator 1 as a center, there being one cathode 2 to eachanode segment, the cathodes being arranged in and at right angles to asecond, larger, concentric circle and each cathode being opposite themiddle of an anode segment. This type of arrangement may be regarded asoperating in a mode corresponding to the zero mode of a conventionalmulti-cavity magnetron, the electrons moving from one anode-cathoderegion to the next in approximately one oscillation of the cavityresonator. This is conventionally indicated in broken lines at the topof Figure 8.

The cathodes and anodes employed in embodiments of this invention may besupported in any convenient way by means which, for reasons ofsimplification, are not shown in the drawings, for example the anodesmay be directly attached to the ends of the cavity 1 and the cathodesmay be attached by means of extensions passing through holes in the endsof the cavity resonator to external supporting structures. Necessarycathode insulation, means for providing hermetic sealing, and outputcircuit means for taking off the generating high frequency power are, ofcourse, provided in any convenient manner and are again not shown.

A split anode magnetron system as disclosed herein is broadly anymagnetron in which the anodes are made up of two parts which may be tworod-like members as well as two segmental members.

While I have described my invention in certain preferred embodiments, Irealize that modifications may be made, and I desire that it beunderstood that no limitations upon my invention are intended other thanmay be imposed by the scope of the appended claims.

I claim:

1. A magnetron comprising a hollow cavity resonator, means for excitinga standing wave in said cavity resonator, said means comprising aplurality of split anode magnetron systems eccentrically mounted withinsaid cavity resonator, each of said systems including a cathode and twoanode segments, said segments consisting of semicylindrical membersspaced at their opposite lineal edges along diametrical lines throughsaid cavity resonator and means for effecting the withdrawal of usefulpower from said cavity resonator.

2. A magnetron as set forth in claim 1 wherein said hollow cavityresonator is cylindrical in shape and wherein said plurality of splitanode magnetron systems are equally spaced along an imaginary ringwithin said cavity resonator and have the cavity resonator axis as acenter, the cathodes of said split anode magnetron systems extendingparallel to and spaced from the cavity resonator axis, and wherein eachof said pairs of anode segments have the associated cathode located attheir common axis.

References Cited in the file of this patent UNITED STATES PATENTS2,063,342 Samuel Dec. 8, 1936 2,084,867 Prinz et al June 22, 19372,241,976 Blewett et al. May 13, 1941 2,429,291 Okress Oct. 21, 19472,617,079 McNall Nov. 4, 1952

